Patent Application
20250034985
This invention relates generally to the field of submersible pumping systems, and more particularly, but not by way of limitation, to a system and method for determining and correcting downhole temperature measurements.
Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including an electric motor coupled to one or more high performance pump assemblies. Production tubing is connected to the pump assemblies to deliver the petroleum fluids from the subterranean reservoir to a storage facility on the surface.
The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly one hundred feet, and may be rated up to hundreds of horsepower. Typically, electricity is generated on the surface and supplied to the motor through a heavy-duty power cable. The power cable typically includes several separate conductors that are individually insulated within the power cable.
It is important to monitor the temperature of the motor during operation of the downhole pumping system. Thermocouples and resistance temperature detectors (RTDs) have been used as temperature sensors to measure the temperature of the motor by placing the sensor in close proximity to the windings of the motor. The leads from the temperature sensor are typically connected in the field to a downhole sensor module (or gauge) attached to the motor. The sensor module collects the output from the temperature sensor and reports the temperature reading to the operator on the surface.
Through installer error, the leads from the temperature sensor can be incorrectly connected to the sensor module. It can be difficult to visually identify the polarity of the leads and the corresponding connectors in the sensor module, particularly in remote environments with poor lighting. If the leads from the temperature sensor are unintentionally reversed when they are connected to the sensor module, the output signal generated by the temperature sensor can be reversed or altogether absent. In certain cases, the erroneous temperature measurements cause the operator to pull the pumping system to investigate and correct the faulty connection between the temperate sensor and the sensor module.
There is, therefore, a need for an improved temperature sensor system that identifies and corrects improperly connected temperature sensors and determines if the temperature sensor is no longer operational. The present disclosure is directed to these and other deficiencies in the prior art.
In one aspect, embodiments of the present disclosure are directed to a method for measuring the temperature of a motor used in a submersible pumping system. In these embodiments, the method includes the steps of obtaining an analog motor temperature signal from a motor temperature sensor, converting the analog motor temperature signal to a digital motor temperature signal using an analog-to-digital converter (ADC), providing the digital motor temperature signal to a processor, determining the absolute value of the digital motor temperature signal with the processor to produce a corrected digital motor temperature signal, and reporting the corrected digital motor temperature signal.
In other aspects, the present disclosure is directed to a method for measuring the temperature of a motor used in a submersible pumping system where the method includes the steps of connecting a motor temperature sensor to a temperature sensor circuit in a sensor module, connecting the sensor module to the motor, deploying the pumping system into a wellbore, energizing the motor with a motor drive, obtaining an analog motor temperature signal from the motor temperature sensor, converting the analog motor temperature signal to a digital motor temperature signal using an analog-to-digital converter (ADC) within the temperature sensor circuit, providing the digital motor temperature signal to a processor within the temperature sensor circuit, determining the absolute value of the digital motor temperature signal with the processor to produce a corrected digital motor temperature signal, and reporting the corrected digital motor temperature signal to the motor drive.
In yet other embodiments, the present disclosure is directed to method for measuring the temperature of a motor within a submersible pumping system. In these embodiments, the method begins with the step of performing a sensor test using a motor temperature sensor circuit. If the motor temperature sensor is detected, the method continues with the step of determining the type of the motor temperature sensor and then measuring the temperature of the motor with the motor temperature sensor. If, on the other hand, a motor temperature sensor is not detected, the method continues with the step of measuring the temperature of the motor with a cold junction temperature reference within the motor temperature sensor circuit.
In accordance with an exemplary embodiment of the present invention,
The wellbore 104 includes a casing 108, which has perforations 110 that permit the exchange of fluids between the wellbore 104 and the geologic formation 106. Although the downhole pumping system 100 is depicted in a vertical well, it will be appreciated that the downhole pumping system 100 can also be used in horizontal, deviated, and other non-vertical wells. Accordingly, the terms “upper” and “lower” should not be construed as limiting the disclosed embodiments to use in vertical wells.
The production tubing 102 connects the pumping system 100 to a wellhead 112 located on the surface 114, which may be onshore or offshore. Although the pumping system 100 is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids.
The pumping system 100 includes a pump 116, a motor 118 and a seal section 120. The motor 118 is an electric motor that receives its power from a surface-based supply through a power cable 122 and one or more motor lead extensions 124. In many embodiments, the power cable 122 and motor lead extension 124 are configured to supply the motor 118 with three-phase electricity from a surface-based variable speed (or variable frequency) motor drive 126, which receives electricity from a power source 128. The electricity is carried along separate conductors (not separately designated), which each correspond to a separate phase of the electricity. The motor lead extension 124 connects to the motor 118 through a connector 130, which is often referred to as a “pothead” connector. The motor lead extension 124 extends into the pothead 130, where it terminates in a connection to the conductor leads of the motor 118. The pothead connector 130 relieves mechanical stresses between the motor lead extension 124 and the motor 118, while providing a sealed connection that prevents the ingress of wellbore fluids into the motor 118, motor lead extension 124, or pothead 130.
The motor 118 converts the electrical energy into mechanical energy, which is transmitted to the pump 116 by one or more shafts. The pump 116 then transfers a portion of this mechanical energy to fluids within the wellbore 104, causing the wellbore fluids to move through the production tubing 102 to the surface 114. In some embodiments, the pump 116 is a turbomachine that uses one or more impellers and diffusers to convert mechanical energy into pressure head. In other embodiments, the pump 116 is a progressive cavity (PC) or positive displacement pump that moves wellbore fluids with one or more screws or pistons.
The seal section 120 shields the motor 118 from mechanical thrust produced by the pump 116. The seal section 120 is also configured to prevent the introduction of contaminants from the wellbore 104 into the motor 118, while also accommodating the thermal expansion and contraction of lubricants within the motor 118. Although only one pump 116, seal section 120 and motor 118 are shown, it will be understood that the downhole pumping system 100 could include additional pumps 116, seal sections 120 or motors 118.
The pumping system 100 also includes a gauge or sensor module 132 connected to the motor 118. As depicted in
As illustrated in
The motor 118 includes a motor temperature sensor 142. In exemplary embodiments, the motor temperature sensor 142 is configured to measure the internal temperature of the motor 118 and can be attached to the stator assembly 138 or positioned elsewhere in the motor 118 in a position where it can remain immersed in the motor fluid. In some embodiments, the motor temperature sensor 142 is a thermocouple that detects the temperature of the motor lubricating oil or stator windings in the motor 118. In other embodiments, the motor temperature sensor 142 is a resistance temperature detector (RTD), such as a platinum resistance temperature detector. In some embodiments, the motor 118 includes multiple motor temperature sensors 142 and multiple types of motor temperature sensors.
The motor temperature sensor 142 is configured to output a signal representative of the internal operating temperature of the motor 118 to a processing board 144 within the sensor module 132. The motor temperature sensor 142 includes positive and negative sensor leads 146+, 146− that extend through the motor housing 134, where they are connected to corresponding positive and negative sensor module leads 148+, 148−. In
Turning to
The processor 152 outputs a corrected digital temperature signal on output line 166, which can be connected to downstream processors or communication modules configured to report the corrected digital temperature signal to the motor drive 126 or other control and monitoring systems on the surface 114. In certain modes of operation, the processor 152 selectively activates the bias voltage source 156 and current source 158. It will be appreciated that the circuit depicted in
Turning to
At step 206, the processor 152 determines the absolute value of the digital motor temperature signal. In the digital domain, the determination of the absolute value of the digital temperature signal is a relatively straightforward calculation that can be accomplished through a variety of routines that are capable of being performed by the processor 152. The method 200 concludes at step 208 when the processor 152 outputs a corrected digital motor temperature signal along output line 166. In this way, the sensor module 132 is configured to report a corrected digital motor temperature signal that regardless of whether the sensor leads 146+, 146− and sensor module leads 148+, 148− were properly connected. This presents a significant advancement over prior systems that were unable to correct a mismatch in the polarity between the motor temperature sensor 142 and the sensor module 132. Although the method 200 is disclosed in connection with the correction of the output from the motor temperature sensor 142, it will be appreciated that the method 200 could also be applied to other analog sensors within the pumping system 100.
In addition to conveniently correcting the output from the motor temperature sensor 142, the processor 152 can also be configured to perform a sensor identification test 300. In some motors 118, the motor temperature sensor 142 is a thermocouple, while in other motors 118 the temperature sensor 142 is a resistance temperature detector (RTD). During the connection of the sensor module 132 to the motor 118, the installer may not be able to determine which sensor type is present from looking only at the sensor leads 146+, 146−. Once the sensor module 132 is connected and the pumping system 100 has been installed in the wellbore 104, it may be difficult to determine from the signals produced by the sensor module 132 if the motor temperature sensor 142 is faulty, disconnected or an unexpected type.
Turning to
If the ADC voltage is greater than 0.19 volts at step 304, the method 300 moves to step 310, where the processor 152 determines if the ADC voltage (Vadc) is less than 0.4 volts. If the ADC voltage under the test current is less than 0.4 volts, the process moves to step 312 where the processor 152 identifies the motor temperature sensor 142 as a resistance temperature detector (RTD). The processor 152 can then adjust its operation to match the expected output from the resistance temperature detector.
If, however, the voltage at the ADC 154 is not less than 0.4 volts at step 310, the method 300 moves to a break condition process 312. In the break condition process 312, the processor 152 disables the test current at step 314 and reports that an open circuit exists at step 316. This condition could arise, for example, if the motor temperature sensor 142 is not connected to the temperature sensor circuit 150 or if the motor temperature sensor 142 is faulty. Once the processor 152 determines that a break condition exists, the method 300 moves to step 318 where the processor 152 pulls the signal from the cold junction temperature reference 160 as a proxy for the missing output from the motor temperature sensor 142. In some cases, the temperature from the cold junction temperature reference 160 can be interpreted and adjusted to provide a relatively close approximation of the internal motor temperature.
It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.
